JUDY WOODRUFF: The president and his administration continued to defend and explain their approach to the health care law and its troubled website today.President Obama met at the White House this afternoon with 16 senators on that subject, a dozen of them Democrats, and most facing competitive reelection contests in 2014.Earlier, on Capitol Hill, the Cabinet secretary overseeing the new law ran into tough questions again.NewsHour congressional correspondent Kwame Holman reports.

KATHLEEN SEBELIUS, U.S. Health and Human Services Secretary: Now, some have asked, why not just delay implementation of the new law until all of the problems are fixed?

KWAME HOLMAN: Kathleen Sebelius conceded today there's pressure to extend the six-month period to enrollfor health coverage. But the health and human services secretary insisted it's not the answer.

KATHLEEN SEBELIUS: Delaying the Affordable Care Act wouldn't delay people's cancer or diabetes or Parkinson. It doesn't delay the higher cost all of us pay when uninsured Americans are left with no choice but to rely on emergency rooms for care. So, for millions of Americans, delay is not an option.

KWAME HOLMAN: Sebelius emphasized there have already been significant improvements to the healthcare.govwebsite, but she acknowledged it's a huge job.

KATHLEEN SEBELIUS: I would say there are a couple of hundred functional fixes that have been identified,and they are in priority grouping. It's a pretty aggressive schedule to get to the entire punch list.

KWAME HOLMAN: But the secretary faced skepticism that her agency can meet that timetable. The Senate Finance Committee's Democratic chairman, Max Baucus, suggested the administration's track record isn't good.

SEN. MAX BAUCUS, D-Mont.: I want it to work. I want to do what I can to help you make it work. But thatmeans you also have to -- it's a two-way street. You have to tell us what's going on, candidly, fully, totally...

KATHLEEN SEBELIUS: Yes.

MAX BAUCUS: ... so we don't wake up into November, lo and behold, still not there yet.

KWAME HOLMAN: Some Republicans said it's already too late for promises. Fellow Kansan Pat Roberts told Sebelius there's only thing for her to do at this point.

SEN. PAT ROBERTS, R-Kan.: In your zeal to implement this law, not warnings, not advice, not counsel would deter you from implementing the exchanges. You have said America should hold you accountable, which is whytoday, Madam Secretary, I repeat my request for you to resign.

KWAME HOLMAN: Republicans also stepped up their criticism that insurance companies are canceling hundreds of thousands of policies, and possibly more than three million, according to one report, despite the president's promise to the contrary.

Wyoming Senator Mike Enzi:

SEN. MICHAEL B. ENZI, R-Wyo.: Henry Ford said that customers could have his Model T in any color they wanted, so long as it was black. Sounds similar to what the president's promised with health care.

KATHLEEN SEBELIUS: Well, Senator, I think that the president's promise was in the law from the day it was written, and that is the grandfather clause that we wrote as a policy, which basically said that plans that were in effect in March of 2010 that didn't change to the detriment of the consumer -- even though theinsurance company could raise premiums, they couldn't eliminate benefits or take away items that the consumer liked -- that those are in effect, and they can stay in effect.

KWAME HOLMAN: Today's Capitol Hill hearing came amid reports federal and state officials are asking health insurers to cut back on policy terminations. One company now says it will extend existing coverage for about 100,000 customers by three months.

Still, the Obama administration is resisting bipartisan calls to have Congress block the policy terminations altogether.White House spokesman Jay Carney said yesterday enacting such a provision would undercut thegoals of the health care law.

JAY CARNEY, White House Press Secretary: If you're going to assert that insurance companies can continue to offer substandard plans, bad apple plans, for example, that undermines the -- the fundamental promise of the Affordable Care Act, which is that everyone in America should have access to affordable, qualityhealth care coverage.

KWAME HOLMAN: President Obama himself took his pitch for the program on the road today. He traveled to Dallas to meet with volunteers helping Americans enroll in the online insurance marketplace.